1. Field of the Invention
The present invention relates to a communication module for a means of transportation, and more particularly to a communication module which is used for measurement of the distance and/or the relative speed between a means of transportation such as an automobile, a vessel or the like and another means of transportation ahead or behind, or for communication between means of transportation.
2. Description of Related Art
Now, an automobile is given as an example of means of transportation. A communication module is provided in the front or the rear side of an automobile in order to measure the distance and the relative speed between the automobile and another automobile ahead or behind. The communication module comprises a Gunn oscillator, a circulator, a directional coupler, a mixer and an antenna. For a high performance communication system, an antenna which has a high directivity and a large gain, that is, an antenna with large dimensions is required to reduce the S/N ratio (signal-to-noise ratio) and the C/N ratio (carrier-to-noise ratio). Accordingly, the communication module occupies a large area of the front or the rear side of an automobile, which ruins the appearance of the automobile.